The present invention relates to a device and method for automatically supplying molten metal, and more particularly, to the automatic supplying device and the supplying method for successively supplying a molten metal to a metal mold having a small volume.
For automatically supplying a molten metal having a small volume such as from 5 grams to several hundreds grams to a casting port of a die-casting machine, it would be generally difficult to maintain accuracy of molten metal supplying amount and to prevent temperature of the supplied molten metal from being lowered.
In order to overcome this problem, several proposals have been made. For example, Japanese Utility Model Application Kokai No. 55-55256 discloses a ladle for transferring a molten metal. An upper open end of the ladle is covered with a lid formed with a hole, and a center portion of a bottom of the ladle is formed with a molten metal intake/discharge port. A tube is provided having one end connected to the hole, and another end connected to an opening/closing valve so as to selectively communicate an internal space of the ladle with an atmosphere. If the opening/closing valve is opened, the molten metal can be flowed into the ladle, and if the opening/closing valve is closed, the molten metal in the ladle can be transferred. If the valve is again opened, the molten metal in the ladle is discharged into a casting port of a die-casting machine. Further, a vacuum suction means is connected to the opening/closing valve for providing negative pressure within the ladle so as to enhance suction efficiency of the molten metal thereinto and to prevent the molten metal from being dripped from the ladle during its transfer.
According to the above described conventional molten metal supplying device, since pouring is performed by introducing the atmospheric pressure into the ladle through the opening/closing valve and by making use of own weight of the molten metal, relatively prolonged time may be required for pouring. Therefore, a shot cycle is prolonged to lower productivity. Since the shot cycle is prolonged, temperature of the molten metal within the ladle is promptly decreased if a small amount of the molten metal is carried in the ladle. Accordingly, quality of die-casting product may be degraded. Further, since the pouring is performed by the weight of the molten metal, a finally discharged molten metal may be suspended from the intake/discharge port in the form of an icicle. If the suspended molten metal is solidified, subsequent operation may not be achievable. Furthermore, if the icicle formed residual molten metal is dropped down during returning stroke of the ladle toward the molten metal intaking position, the dropped and accumulated molten metal at the moving path of the ladle may prevent the ladle from being transferred.